Today for the first time and since almost two months playing every day I've seen that during a duel the PC fan (or the GPU one) has started to speed up really loud without apparent reason, in the middle of a game. I have experienced it again in a second game, no particular crowded game nor any special effect or reason that I hadn't seen previously.

Is there any report on this behaviour? What I've seen is that once I logout the fan stops being so loud.

Hello,
The game has not updated recently, so unless you've changed the mode you're playing or something, I'm not sure what the game can be doing to cause this.
You could try lowering the graphics quality and seeing if the problem goes away, I guess, or I think people suggest VSYNC can either help or make stuff worse. Both are available via the "cog" menu.

I think historically the air elemental was "difficult" for the game to draw, but I think that may have gone away some time ago.

Fortunately, I rebooted the PC yesterday after that and there was no buzz again during a play. Notice that that sound persisted even when I left the game I was playing but ended at the moment I logged out from the network. Maybe it was something interacting badly with on line applications in the background (I was worried in case some malware was mining bitcoins using my cheap brand new GPU... ).

The GPU is new and is able to handle the graphics requirements and the PSU should endure at least a couple of years without any problems. I hope it was just something spurious.

Sometimes, almost once per game, I notice a minimal stop in the game flow when a FX effect has to appear, say paralysis, some summon, but it is not something to be worried about.

Hey there Roderic, I want to point out that I've had similar behavior with Chaos Reborn since the first time I played (so for me it's always been present, even when playing with different computers)

For me the solution has always been to just play in short sessions. I always suspected it was something about the graphics code in the game (or in how Unity handles graphics) because as RafiRomero described, it was much worse during the first months after the introduction of the air elemental. I had a laptop that seemed to overheat dangerously, and a PC that would shut down when playing for more than 30 minutes ... Now I don't use that one to play chaos hehe

To make it clear, even if some things make the problem worse, for me this problem is constant from the moment I start the game to the moment I close it (well, not immediately after closing because it takes some minutes for it to cool down). But it hasn't stopped me from playing 658 hours total